Fire extinguishing foam stabilizer



Patented Apr. 29, 1952 FIRE EXTINGUISHIN G FOAM STABILIZER Joseph M.Perri, Philadelphia, Pa., assignor to National Foam System, Inc.,Philadelphia, Pa., a corporation of Delaware N Drawing. ApplicationSeptember 9, 1948, Serial No. 48,529

This invention relates generally to fire extinguishing compositions andmore particularly to such compositions as are capable, when combinedwith water, of producing a foam nonsupporting to combustion and whichserves as a blanket to smother and so extinguish the flames produced byburning organic liquids having high capillary characteristics, such asalcohols, ethers, acetones, organic esters and the like. Morespecifically, the present invention relates to a chemical foam chargedesigned for use in portable extinguishers of the type containingsolutions of acid and basic foam-forming agents which are normallymaintained separate but are adapted to be mixed together to produce astabilized fire extinguishing foam.

Heretofore and prior to this invention, various foam-formingcompositions have been employed a in portable extinguishers forproducing, upon reaction thereof, a foam satisfactory for theextinguishment of oil and gasoline fires. These compositions ordinarilycomprise aqueous solutions of sodium bicarbonate and aluminum sulphate,into one orv the otherv of which is incorporated a suitable stabilizerfor increasing the surface viscosity of the foam bubbles formed when theacid and basic reagents are mixed together.

While the foam produced by such conventional- 1y charged extinguishersis quite effective in extinguishing oil, gasoline and the like fires,experience has demonstrated that such foam is totally ineffective as anextinguisher of such fires as are produced by burning alcohols, esters,ketones, ethers, acetones and other such flammable organic liquids, thisprimarily for the reason that ordinary stabilized fire extinguishingfoam is quickly broken down and disintegrated by organic liquidscontacted by the foam.

In order to obviate this difficulty attempts have been made toincorporate as a stabilizer in one or the other of the aqueous acid andbasic foamforming agents a material which results, upon reaction of saidagents, in the formation of a water insoluble aluminum soap, it havingbeen found that the presence of such soap in the reacted foam-formingsolution produces a stabilized foam which is not. materially affected byalcohol and other such organic liquids and which will float freely uponthe surface thereof in such quantities as to produce an effective fireextinguishing foam blanket. 7

It is known that an alkanol amino soap may be utilized for forming thedesired Water insoluble aluminum soap, such soap being readily obtainedby mixing coconut fatty acids with an amine,

3 Claims. (Cl. 252-6.5)

such as monoethanol amine, triethanolamine or diethanolamine. However,when such alkanol amino soap is mixed with water, as when incorporatedin a water solution of bicarbonate of soda, there results the formationof an insoluble curd which is comprised of calcium or magnesium soap,when hard water is used, and some alkanol amine soap salted out by thesaturated bicarbonate solution, such curd having a tendency to rise tothe top of the solution in the form of a gel or liver. The presence ofthese curds in a water solution of the basic foam-forming agent in aportable extinguisher for chemically producing fire extinguishing foamseriously interferes with efiective operation of the extinguisher andfor this reason it has been inadvisable and impractical to incorporatethe alkanol amino soap as a foam stabilizer in portable fireextinguishers.

I have found that the above difiiculty may be overcome by incorporatinglecithin with the alkanol amino soap in the water solution of thebicarbonate of soda. The lecithin, as employed in accordance with thepresent invention, prevents the formation of the undesired curds or gelby rendering the insoluble soap capable of being supported in solutionin a colloidal condition. In the presence of the lecithin, thesub-microscopic particles of the alkanol amino soap are completely andhomogeneously dispersed throughout the aqueous solution of the sodiumbicarbonate in the extinguisher, thus maintaining the latter free of anygel or liver formation which might interfere with or constitute a hazardto eflicient operation of the extinguisher when said basic solution iscombined with the acid (aluminum sulphate) solution to produce thedesired fire extinguishing foam. I

In the preparation of the stabilizer of the pres- I ent invention, theseveral ingredients thereof are combined substantially in the followingproportions and in accordance with the following procedure:

First, 25 grams of lecithin are dissolved in 30 cc. of isopropanol. Tothis solution is then added approximately 33 grams of coconut fattyacids, 10 cc. of monoethanolamine and 185 cc. of water, the whole beingthoroughly mixed at a maintained temperature of between to degrees F.While this higher temperature is preferred for the mixing operation, themixing may be efiected at room temperature, and accordingly it will beunderstood that thetemperature maintained during the mixing operation isnot in any sense critical. In place of the monoethanol- 3 amine, eitherdiethanolamine or triethanolamine may be employed.

The coconut fatty acids combine with the amine to form an alkanol aminosoap, which latter is completely and homogeneously dispersed in themixture prepared as above described by the action of the lecithinpresent in said mixture, the final mixture being in the form of acolloidal dispersion.

In the use of the stabilizer of the present invention in a 2 gallonacid-basic fire extinguisher, the following charge formula is preferredand recommended:

For the acid charge, 30 ounces of aluminum sulphate is dissolved in 2%;pints of water.

For the basic charge, 25 ounces of bicarbonate of soda is dissolved in1% gallons of water and to this solution is added 4 ounces of thestabilizer prepared as above described.

Upon operation of the extinguisher, the acid and basic charges arecombined and react .to produce a stabilized foam capable ofextinguishing not only fires of gasoline and related petroleum products,but also fires of methanol, acetone, ethylacetate, isopropyl alcohol,isopropyl ether and other such polar liquids normally incapable of beingextinguished by ordinary foam. The more or less water soluble alkanol.amino soap present in the basic charge and colloidally .dispersedtherein by the lecithin to prevent the formation of any curds or gelwhich might interfere with efiicient operation of the extinguisher, uponreaction of said basic charge with the acid charge, is converted to awater insoluble aluminum soap which renders the foam capable ofextinguishing fires of alcohol and other such flammable organic liquidsof high capillary characteristics.

What is claimed as new and useful is:

1. A stabilizer for a fire-extinguishing foam obtained by combining anaqueous solution of aluminum sulphate with an aqueous solution ofbicarbonate of soda, said stabilizer consisting of an alkanol amino soapcolloidally dispersed by 4 lecithin in one of said foam-formingsolutions.

2. In a method of extinguishing fires of alcohol and other suchflammable organic liquids of high capillary characteristics, the stepscomprising colloidally dispersing by lecithin an alkanol amino soap inan aqueous solution of bicarbonate of soda and then reacting said basicsolution with an aqueous solution of aluminum sulphate to produce fireextinguishing foam.

3. In a method of extinguishing fires of flammable liquids, the stepscomprising forming an aqueous solution of an alkanol amino soapcolloidally dispersed by lecithin, introducing said aqueous colloidaldispersion in an aqueous solution of sodium bicarbonate, and reactingsaid solution containing said colloidal dispersion with aluminumsulphate to form fire extinguishing foam.

JOSEPH M. PERRI.

REFERENCES CITED The following references are of'recorcl in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,375,779 Crosby et al Apr. 26,1921 1,624,389 Dunlap et a1 Apr. 12, 1927 1,833,899 Hoyt ,Dec. 1, 19312,002,885 Detwiler et a1 Sept. 9, 1932 2,020,517 Rewald Nov. 12, 19352,047,128 Park 1. July 7, 1936 2,057,695 Schwieger Oct. 20, 19362,168,468 Braun et al. Aug. 8, .1939 2,253,587 Goodner Oct. 14, 1941FOREIGN PATENTS Number Country Date 517,812 Great Britain Feb. 9, 1940OTHER REFERENCES Gregory: Uses and Applications of Chemicals and RelatedMaterials, vol. II, pages 185, 186, Reinhold Publishing Corp., N. Y.(1944).

1. A STABILIZER FOR A FIRE-EXTINGUISHING FOAM OBTAINED BY COMBINING ANAQUEOUS SOLUTION OF ALUMINUM SULPHATE WITH AN AQUEOUS SOLUTION OFBICARBONATE OF SODA, SAID STABILIZER CONSISTING OF AN ALKANOL AMONO SOAPCOLLOIDALLY DISPERSED BY LECITHIN IN ONE SAID FOAM-FORMING SOLUTIONS.